The present invention relates generally to ball valves and, more particularly, to ball valves with an externally adjustable seal carrier.
Conventional ball valves generally include a tubular valve body or housing, a rotatable ball disposed within the center of the valve body, annular seals positioned on each side of the ball, and stationary or movable seal carriers for holding the seals in place and forcing the seals tightly against the surface of the ball to prevent leakage of fluid from between the seal carriers and ball. Flow passages through the ball and seal carriers allow the passage of fluid when the ball is rotated into an open position.
Seals wear from usage, and unless means are provided to compensate for the wear, the valve will begin to leak and require disassembly and replacement of the worn seals. To provide such compensating means, particularly in ball valves utilizing connecting sleeves and union nuts, some valves have at least one slidable seal carrier that is externally adjusted by movement of the union nut. Tightening of the union nut, which bears against the connecting sleeve, causes the connecting sleeve to contact and move the seal carrier toward the ball, thereby compensating for seal wear. A ball valve of this general construction is shown in U.S. Pat. No. 3,550,902.
A significant disadvantage of ball valves of this type is the inability to remove the union nut and connecting sleeve from the side of the valve with the slidable seal carrier while maintaining fluid pressure on the opposite side of the valve with the ball in a closed, fluid blocking position. Should the union nut and connecting sleeve be removed under such conditions, as is sometimes necessary to repair or replace a pipe attached to the connecting sleeve, the pressure would blow the ball and seal carrier out of the valve body.
In an attempt to solve this problem, some valves have a seal carrier with a plurality of contact-type dogs and a valve body with cooperating recesses which receive the dogs. The dogs, when inserted in the recesses and twisted, lock the seal carrier within the valve body. To provide for external adjustment of the carrier when locked, the recesses are sized to permit axial movement of the dogs within the recesses. As above, the union nut and connecting sleeve are utilized to accomplish the adjustment. A ball valve of this general construction is shown in U.S. Pat. No. 4,059,250.
Although ball valves of the dog and recess type of construction do prevent the blowout discussed above, they have a significant disadvantage in their inability to provide for adjustment of the seal carrier when the union nut and connecting sleeve are removed. Since no means are provided to hold the seal carrier firmly against the ball except for the union nut and connecting sleeve, leakage may occur when they are removed.
In another attempt to solve the blowout problem, some valves utilize a locking ring arrangement. A spring cam may also be used with this type of valve to urge the seal carrier toward the ball. These ball valves suffer from the same disadvantage as discussed above since they provide no means for adjustment of the seal carrier when the union nut and connecting sleeve are removed. Such adjustment is particularly important when the fluid pressure applied to the valve is great enough to counteract the biasing action of the spring cam. A ball valve of this general construction is shown in U.S. Pat. No. 4,023,773.
It will therefore be appreciated that there has been a significant need for a ball valve with an externally adjustable seal carrier that not only prevents blowout of the ball and seal carrier, but also provides for adjustment of the seal carrier to inhibit leakage when the union nut and connecting sleeve are removed. The present invention fulfills this need, and further provides other related advantages.